SUMMARYThis paper reports an experimental investigation in designing a tree-shaped wind power system using piezoelectric materials. The proposed system has been designed to produce power if there is any wind strong enough to cause any bending in the energy converting elements, i.e. piezoelectric materials. Two different kinds of piezoelectric materials are used in this study to produce power by scavenging energy from the wind. The soft flexible one is used to make the leaf element, whereas the hard one is applied to the trunk portion of the tree requiring rather strong winds to generate any power. Although small, each leaf deems to play the role of a power producer as currents are continuously trickling down to a storage battery installed at the bottom of the system.

Along with the increase in renewable energy, research on energy harvesting combined with piezoelectric energy is being conducted. However, it is difficult to predict the power generation of combined harvesting because there is no data on the power generation by a single piezoelectric material. Before predicting the corresponding power generation and efficiency, it is necessary to quantify the power generation by a single piezoelectric material alone. In this study, the generated power is measured based on three parameters (size of the piezoelectric ceramic, depth of compression, and speed of compression) that contribute to the deformation of a single PZT (Lead zirconate titanate)-based piezoelectric element. The generated power was analyzed by comparing with the corresponding parameters. The analysis results are as follows: (i) considering the difference between the size of the piezoelectric ceramic and the generated power, 20 mm was the most efficient piezoelectric ceramic size, (ii) considering the case of piezoelectric ceramics sized 14 mm, the generated power continued to increase with the increase in the compression depth of the piezoelectric ceramic, and (iii) For piezoelectric ceramics of all diameters, the longer the depth of deformation, the shorter the frequency, and depending on the depth of deformation, there is a specific frequency at which the charging power is maximum. Based on the findings of this study, PZT-based elements can be applied to cases that receive indirect force, including vibration energy and wave energy. In addition, the power generation of a PZT-based element can be predicted, and efficient conditions can be set for maximum power generation.

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